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      <div class="span12">
        <h4 id="title">Icon Sprites with WebGL</h4>
        <p class="tags">
          <span class="badge-group">
            <a href="./index.html?q=webgl" class="badge badge-info">webgl</a><a
              class="badge badge-info tag-modal-toggle" data-bs-toggle="modal" data-bs-target="#tag-example-list"
              data-title="webgl" data-content="&lt;ul class=&quot;list-group&quot;&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./cog-stretch.html&quot;&gt;Band Contrast Stretch&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./cog-style.html&quot;&gt;Change Tile Layer Style&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-draw-line.html&quot;&gt;Draw lines rendered with WebGL&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./heatmap-earthquakes.html&quot;&gt;Earthquakes Heatmap&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./filter-points-webgl.html&quot;&gt;Filtering features with WebGL&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./geotiff-reprojection.html&quot;&gt;GeoTIFF Reprojection&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action active&quot; href=&quot;./icon-sprite-webgl.html&quot;&gt;Icon Sprites with WebGL&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-layer-swipe.html&quot;&gt;Layer Swipe (WebGL)&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./multiple-cogs.html&quot;&gt;Multiple COG sources&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./numpytile.html&quot;&gt;Rendering 16-bit NumpyTiles&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-sea-level.html&quot;&gt;Sea Level (with WebGL)&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-shaded-relief.html&quot;&gt;Shaded Relief (with WebGL)&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-points-layer.html&quot;&gt;WebGL points layer&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-tile-style.html&quot;&gt;WebGL Tile Layer Styles&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-tiles.html&quot;&gt;WebGL Tiles&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-vector-layer.html&quot;&gt;WebGL Vector Layer&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-vector-tiles.html&quot;&gt;WebGL Vector Tiles Layer&lt;/a&gt;
                  &lt;/ul&gt;" tabindex="0">17</a>
          </span>
          <span class="badge-group">
            <a href="./index.html?q=icon" class="badge badge-info">icon</a><a class="badge badge-info tag-modal-toggle"
              data-bs-toggle="modal" data-bs-target="#tag-example-list" data-title="icon" data-content="&lt;ul class=&quot;list-group&quot;&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./animated-gif.html&quot;&gt;Animated GIF&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./filter-points-webgl.html&quot;&gt;Filtering features with WebGL&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./icon-scale.html&quot;&gt;Icon and Label Scale&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./icon-color.html&quot;&gt;Icon Colors&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./modify-icon.html&quot;&gt;Icon modification&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./icon-negative.html&quot;&gt;Icon Pixel Operations&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action active&quot; href=&quot;./icon-sprite-webgl.html&quot;&gt;Icon Sprites with WebGL&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./icon.html&quot;&gt;Icon Symbolizer&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./icon-width.html&quot;&gt;Icon Symbolizer width and height&lt;/a&gt;
                  &lt;/ul&gt;" tabindex="0">9</a>
          </span>
          <span class="badge-group">
            <a href="./index.html?q=sprite" class="badge badge-info">sprite</a><a
              class="badge badge-info tag-modal-toggle" data-bs-toggle="modal" data-bs-target="#tag-example-list"
              data-title="sprite" data-content="&lt;ul class=&quot;list-group&quot;&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./filter-points-webgl.html&quot;&gt;Filtering features with WebGL&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action active&quot; href=&quot;./icon-sprite-webgl.html&quot;&gt;Icon Sprites with WebGL&lt;/a&gt;
                  &lt;/ul&gt;" tabindex="0">2</a>
          </span>
          <span class="badge-group">
            <a href="./index.html?q=point" class="badge badge-info">point</a><a
              class="badge badge-info tag-modal-toggle" data-bs-toggle="modal" data-bs-target="#tag-example-list"
              data-title="point" data-content="&lt;ul class=&quot;list-group&quot;&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action active&quot; href=&quot;./icon-sprite-webgl.html&quot;&gt;Icon Sprites with WebGL&lt;/a&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action&quot; href=&quot;./webgl-points-layer.html&quot;&gt;WebGL points layer&lt;/a&gt;
                  &lt;/ul&gt;" tabindex="0">2</a>
          </span>
          <span class="badge-group">
            <a href="./index.html?q=ufo" class="badge badge-info">ufo</a><a class="badge badge-info tag-modal-toggle"
              data-bs-toggle="modal" data-bs-target="#tag-example-list" data-title="ufo" data-content="&lt;ul class=&quot;list-group&quot;&gt;
                  &lt;li&gt;&lt;a class=&quot;list-group-item list-group-item-action active&quot; href=&quot;./icon-sprite-webgl.html&quot;&gt;Icon Sprites with WebGL&lt;/a&gt;
                  &lt;/ul&gt;" tabindex="0">1</a>
          </span>
        </p>
        <div class="modal modal-tag-example" id="tag-example-list" tabindex="-1" role="dialog"
          aria-labelledby="tag-example-title" aria-hidden="true">
          <div class="modal-dialog modal-dialog-scrollable" role="document">
            <div class="modal-content">
              <div class="modal-header">
                <h5 class="modal-title" id="tag-example-title"></h5>
                <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close"></button>
              </div>
              <div class="modal-body">
                <div class="list-group"></div>
              </div>
            </div>
          </div>
        </div>
        <div id="map" class="map"></div>
        <div>当前目击： <span id="info"></span></div>
        <div>
          <label for="shape-filter">按UFO形状筛选:</label>
          <select id="shape-filter"></select>
        </div>

      </div>
      <form method="POST" id="codepen-form" target="_blank" action="https://codesandbox.io/api/v1/sandboxes/define">
        <input id="codesandbox-params" type="hidden" name="parameters">
      </form>
    </div>

    <div class="row-fluid">
      <div class="span12">
        <p id="shortdesc">Rendering many icons with WebGL</p>
        <div id="docs">
          <p>
            这个示例展示了如何使用<code>ol/layer/WebGLPoints</code>来渲染大量的精灵。上面的地图是基于美国国家不明飞行物报告中心的数据集：每个图标都标记了一次不明飞行物的目击事件，根据其报告的形状（圆盘、灯光、火球等）进行标记。目击事件越老，图标颜色越红。
          </p>
          <p>一个非常简单的精灵集（sprite atlas）被用作 PNG
            文件的形式，其中包含网格上的所有图标。然后，将<code>style</code>对象传递给<code>ol/layer/WebGLPoints</code>构造函数，以根据目击事件的形状指定使用哪个精灵。
          </p>
          <p>该数据集包含约 8 万个点，可以在以下网址找到： <a
              href="https://www.kaggle.com/NUFORC/ufo-sightings">https://www.kaggle.com/NUFORC/ufo-sightings</a></p>
        </div>
      </div>
    </div>

    <div class="row-fluid">
      <h5 class="source-heading">main.js</h5>
      <pre><code id="example-js-source" class="language-js">import Feature from &#x27;ol/Feature.js&#x27;;
import Map from &#x27;ol/Map.js&#x27;;
import Point from &#x27;ol/geom/Point.js&#x27;;
import TileLayer from &#x27;ol/layer/WebGLTile.js&#x27;;
import VectorSource from &#x27;ol/source/Vector.js&#x27;;
import View from &#x27;ol/View.js&#x27;;
import WebGLPointsLayer from &#x27;ol/layer/WebGLPoints.js&#x27;;
import XYZ from &#x27;ol/source/XYZ.js&#x27;;
import {fromLonLat} from &#x27;ol/proj.js&#x27;;

const key &#x3D; &#x27;Get your own API key at https://www.maptiler.com/cloud/&#x27;;
const attributions &#x3D;
  &#x27;&lt;a href&#x3D;&quot;https://www.maptiler.com/copyright/&quot; target&#x3D;&quot;_blank&quot;&gt;&amp;copy; MapTiler&lt;/a&gt; &#x27; +
  &#x27;&lt;a href&#x3D;&quot;https://www.openstreetmap.org/copyright&quot; target&#x3D;&quot;_blank&quot;&gt;&amp;copy; OpenStreetMap contributors&lt;/a&gt;&#x27;;

const map &#x3D; new Map({
  layers: [
    new TileLayer({
      source: new XYZ({
        attributions: attributions,
        url:
          &#x27;https://api.maptiler.com/tiles/satellite/{z}/{x}/{y}.jpg?key&#x3D;&#x27; + key,
        tileSize: 512,
      }),
    }),
  ],
  target: document.getElementById(&#x27;map&#x27;),
  view: new View({
    center: [0, 4000000],
    zoom: 2,
  }),
});

const oldColor &#x3D; [255, 160, 110];
const newColor &#x3D; [180, 255, 200];

const style &#x3D; {
  variables: {
    filterShape: &#x27;all&#x27;,
  },
  filter: [
    &#x27;any&#x27;,
    [&#x27;&#x3D;&#x3D;&#x27;, [&#x27;var&#x27;, &#x27;filterShape&#x27;], &#x27;all&#x27;],
    [&#x27;&#x3D;&#x3D;&#x27;, [&#x27;var&#x27;, &#x27;filterShape&#x27;], [&#x27;get&#x27;, &#x27;shape&#x27;]],
  ],
  &#x27;icon-src&#x27;: &#x27;data/ufo_shapes.png&#x27;,
  &#x27;icon-width&#x27;: 128,
  &#x27;icon-height&#x27;: 64,
  &#x27;icon-color&#x27;: [
    &#x27;interpolate&#x27;,
    [&#x27;linear&#x27;],
    [&#x27;get&#x27;, &#x27;year&#x27;],
    1950,
    oldColor,
    2013,
    newColor,
  ],
  &#x27;icon-offset&#x27;: [
    &#x27;match&#x27;,
    [&#x27;get&#x27;, &#x27;shape&#x27;],
    &#x27;light&#x27;,
    [0, 0],
    &#x27;sphere&#x27;,
    [32, 0],
    &#x27;circle&#x27;,
    [32, 0],
    &#x27;disc&#x27;,
    [64, 0],
    &#x27;oval&#x27;,
    [64, 0],
    &#x27;triangle&#x27;,
    [96, 0],
    &#x27;fireball&#x27;,
    [0, 32],
    [96, 32],
  ],
  &#x27;icon-size&#x27;: [32, 32],
  &#x27;icon-scale&#x27;: 0.5,
};

const shapeSelect &#x3D; document.getElementById(&#x27;shape-filter&#x27;);
shapeSelect.addEventListener(&#x27;input&#x27;, function () {
  style.variables.filterShape &#x3D; shapeSelect.value;
  map.render();
});
function fillShapeSelect(shapeTypes) {
  Object.keys(shapeTypes)
    .sort(function (a, b) {
      return shapeTypes[b] - shapeTypes[a];
    })
    .forEach(function (shape) {
      const option &#x3D; document.createElement(&#x27;option&#x27;);
      const sightings &#x3D; shapeTypes[shape];
      option.text &#x3D; &#x60;${shape} (${sightings} sighting${
        sightings &#x3D;&#x3D;&#x3D; 1 ? &#x27;&#x27; : &#x27;s&#x27;
      })&#x60;;
      option.value &#x3D; shape;
      shapeSelect.appendChild(option);
    });
}

const client &#x3D; new XMLHttpRequest();
client.open(&#x27;GET&#x27;, &#x27;data/csv/ufo_sighting_data.csv&#x27;);
client.addEventListener(&#x27;load&#x27;, function () {
  const csv &#x3D; client.responseText;
  // key is shape name, value is sightings count
  const shapeTypes &#x3D; {};
  const features &#x3D; [];

  let prevIndex &#x3D; csv.indexOf(&#x27;\n&#x27;) + 1; // scan past the header line
  let curIndex;
  while ((curIndex &#x3D; csv.indexOf(&#x27;\n&#x27;, prevIndex)) !&#x3D;&#x3D; -1) {
    const line &#x3D; csv.substring(prevIndex, curIndex).split(&#x27;,&#x27;);
    prevIndex &#x3D; curIndex + 1;

    const coords &#x3D; [parseFloat(line[5]), parseFloat(line[4])];
    const shape &#x3D; line[2];
    shapeTypes[shape] &#x3D; (shapeTypes[shape] || 0) + 1;

    features.push(
      new Feature({
        datetime: line[0],
        year: parseInt(/[0-9]{4}/.exec(line[0])[0], 10), // extract the year as int
        shape: shape,
        duration: line[3],
        geometry: new Point(fromLonLat(coords)),
      })
    );
  }
  shapeTypes[&#x27;all&#x27;] &#x3D; features.length;
  map.addLayer(
    new WebGLPointsLayer({
      source: new VectorSource({
        features: features,
        attributions: &#x27;National UFO Reporting Center&#x27;,
      }),
      style: style,
    })
  );
  fillShapeSelect(shapeTypes);
});
client.send();

const info &#x3D; document.getElementById(&#x27;info&#x27;);
map.on(&#x27;pointermove&#x27;, function (evt) {
  if (map.getView().getInteracting() || map.getView().getAnimating()) {
    return;
  }
  const text &#x3D; map.forEachFeatureAtPixel(evt.pixel, function (feature) {
    const datetime &#x3D; feature.get(&#x27;datetime&#x27;);
    const duration &#x3D; feature.get(&#x27;duration&#x27;);
    const shape &#x3D; feature.get(&#x27;shape&#x27;);
    return &#x60;On ${datetime}, lasted ${duration} seconds and had a &quot;${shape}&quot; shape.&#x60;;
  });
  info.innerText &#x3D; text || &#x27;&#x27;;
});
</code></pre>
    </div>

    <div class="row-fluid">
      <h5 class="source-heading">index.html</h5>
      <pre><code id="example-html-source" class="language-markup">&lt;!DOCTYPE html&gt;
&lt;html lang="en"&gt;
  &lt;head&gt;
    &lt;meta charset="UTF-8"&gt;
    &lt;title&gt;Icon Sprites with WebGL&lt;/title&gt;
    &lt;link rel="stylesheet" href="node_modules/ol/ol.css"&gt;
    &lt;style&gt;
      .map {
        width: 100%;
        height: 400px;
      }
    &lt;/style&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;div id&#x3D;&quot;map&quot; class&#x3D;&quot;map&quot;&gt;&lt;/div&gt;
    &lt;div&gt;Current sighting: &lt;span id&#x3D;&quot;info&quot;&gt;&lt;/span&gt;&lt;/div&gt;
    &lt;div&gt;
      &lt;label for&#x3D;&quot;shape-filter&quot;&gt;Filter by UFO shape:&lt;/label&gt;
      &lt;select id&#x3D;&quot;shape-filter&quot;&gt;&lt;/select&gt;
    &lt;/div&gt;

    &lt;script type="module" src="main.js"&gt;&lt;/script&gt;
  &lt;/body&gt;
&lt;/html&gt;</code></pre>
    </div>

    <div class="row-fluid">
      <h5 class="source-heading">package.json</h5>
      <pre><code id="example-pkg-source" class="language-json">{
  &quot;name&quot;: &quot;icon-sprite-webgl&quot;,
  &quot;dependencies&quot;: {
    &quot;ol&quot;: &quot;8.2.0&quot;
  },
  &quot;devDependencies&quot;: {
    &quot;vite&quot;: &quot;^3.2.3&quot;
  },
  &quot;scripts&quot;: {
    &quot;start&quot;: &quot;vite&quot;,
    &quot;build&quot;: &quot;vite build&quot;
  }
}</code></pre>
    </div>
  </div>

  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/js/bootstrap.bundle.min.js"></script>
  <script src="common.js"></script>
  <script src="icon-sprite-webgl.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.28.0/components/prism-core.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.28.0/plugins/autoloader/prism-autoloader.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.28.0/plugins/toolbar/prism-toolbar.min.js"></script>
  <script
    src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.28.0/plugins/copy-to-clipboard/prism-copy-to-clipboard.js"></script>
  <script src="./resources/common.js"></script>
  <script>
    document.getElementById('tag-example-list')
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</body>

</html>